Dropbox seeking to raise $500 million in stock market debut

One of the world's largest online services for backing up documents, photos and other video is opening its files in an initial public offering of stock.

Dropbox is hoping to raise $500 million in an IPO that comes 11 years after it started in San Francisco. The company confidentially filed for its IPO in October, but the information didn't become publicly available until Friday.

The filing reveals Dropbox has lost more than $1 billion since its inception. That includes a loss of $112 million on revenue of $1.1 billion last year.

Dropbox boasts about 500 million registered users, but most of them don't pay for its service. Only 11 million users pay for premium version of Dropbox's service, a figure that the company is aggressively trying to increase.

That won't be easy, given the fierce competition it's facing. Its rivals in online file storage include three of the world's most powerful companies — Google, Microsoft and Amazon. A smaller competitor, Box Inc., went public at $14 per share two years ago and the stock shot to $23.23 in its first day of trading. It closed Friday at $23.32.

Dropbox hasn't yet disclosed how much of its stock will be sold in the IPO, nor the price for each share. That will occur during the next few weeks as its bankers gauge investor demand. The IPO is likely to attract a lot of attention because Dropbox's service is so widely used.